Conventionally, an air mattress for preventing decubitus ulcers such as that disclosed in patent document 1 and 2 is known. Patent document 1 discloses an air mattress formed by a plurality of bladder-shaped air cells disposed upon a base sheet, wherein all of the air cells are divided into an upper layer and a lower layer by a divider, and all of the air cells are respectively inflated or deflated in the upper layers and lower layers thereof.
Patent document 2 discloses a technique of providing a plurality of air cells within the interior of a retaining member formed from an elastic material so as to line up in the lengthwise direction of the air mattress and adjusting the pressure within the air cells, thereby preventing decubitus ulcers.
Patent document 3 discloses a technique of preventing repelling force from being placed by a mattress upon a location of a person lying on the air mattress at which decubitus ulcers have occurred, and discloses lining up multiple cuboid air cells in the lengthwise direction and widthwise direction of an air mattress, attaching a magnetic marker to a location of a person at which decubitus ulcers have occurred, detecting the position of the marker by means of a magnetic sensor provided in each of the air cells, and reducing the pressure in the air cells corresponding to the position of the detected marker.